Unsaturation alkylene oxides

On the basis of this principle, a process involving oxidation of unsaturated hydrocarbons and other organic compounds, more readily oxidized than alkenes, contribute substantially to solving problems in direct single-stage production of propylene and higher alkylene oxides. 

We shall consider in the present review only some typical addition homopolymers, obtained from unsaturated monomers by opening of >C=C< double bonds therefore, we shall exclude those polymers, such as polyglycols, that, even though may be considered addition polymers, being formed from alkylene oxides, can formally be included in condensation polymers. 

Simple addition, in which both fragments of the NH molecule enter the new compound as in the preparation of alkanolamines from alkylene oxides, aminonitriles from unsaturated nitriles, and ureas and thioureas from isocyanates and isothiocyanates. 

Bogdal et al. have obtained unsaturated polyesters in polyaddition reactions of alkylene oxides such as epichlorohydrin and acid anhydrides (maleic and phthalic anhydrides) in the presence of lithium chloride as catalyst under microwave irradiation conditions (Scheme 14.22) [51, 52]. In the standard procedure, a mixture of 0.10 mol phthalic anhydride and 0.10 mol maleic anhydride with 0.010 mol ethylene glycol, 0.20 mol epichlorohydrin, lithium chloride (0.1% w/w) was placed in a... 

The preparation methods for the synthesis of unsaturated and saturated polyester resins were also elaborated for micro-wave conditions. In the polyaddition reactions of alkylene oxides (i.e., epichlorohydrin) and acid anhydrides (i.e., maleic and phthalic anhydrides), unsaturated polyesters were prepared in the presence of lithium chloride as a catalyst (Figure 30). In comparison with polycondensation reactions of acid anhydrides with diols, these reactions proceed without the release of by-products. 

ASTM D2849-69, Standard Methods of Testing Urethane Foam Polyol Raw Materials, describes a number of tests used for analyzing poly(alkylene oxide)s (1). These tests include metals analysis, acid and hydroxyl numbers, unsaturation values, water, suspended matter, specific gravity, viscosity, and color. Many of these tests are well known and will not be described. Those tests dealing with end groups—i.e., the functional groups that are used in the further reaction of poly(alkylene oxide)s—are discussed below. Detailed test procedures can be found in the cited reference and also can be obtained from poly(alkylene oxide) suppliers. 

In Chapter 4, mechanisms by which carbon-to-carbon unsaturation can be introduced onto the ends of poly (alkylene oxide)s were described. Since these end groups can have a deleterious effect on the performance characteristics of polyurethane foams or elastomers, as well as on other derivatives, the degree of unsaturation is a specification often required by manufacturers or a tool for understanding lot-to-lot variation in products produced. 

ASTM D2849 describes a method in which the poly(alkylene oxide)s are reacted with mercuric acetate and methanol in a methanolic solution. The reaction produces acetoxymercuric-methoxy compounds and acetic acid. The acetic acid produced, which is directly proportional to the amount of unsaturation, is determined by titration with alcoholic potassium hydroxide in the presence of a phenolphthalein indicator. As is the case with other acidimetric titrations, a suitable correction must be made if the starting sample is not neutral to the indicator. 

Finally, conversion of a ketone into the corresponding a-selenoalkyl-lithium and subsequent reaction with alkylene oxide and Jones oxidation results in homologation to furnish an a,/8-unsaturated ketone (Scheme 26). ... 

Polymerizations of unsaturated monomers, such as olefins, vinyl monomers, or acetylenes, exclusively proceed as KC reaction sequences. With exception of crystalline polyethylene, the resulting polymers are thermodynamically unstable, because the corresponding cyclohexanes or benzenes are more stable, but equilibration catalysts do not exist. As soon as polymer backbones include heteroatoms, equilibration reactions become possible, and many polymers may be prepared by KC and by TC polymerizations. An interesting case is synthesis and polymerization of oxiranes. Their synthesis from )S-bromoalcohols and their polymerization via anionic or coordination insertion catalysts represent KC reactions. Yet, heating of oxiranes or poly(alkylene oxides)s with strong protic acids yields the thermodynamically more stable 1,4-dioxanes. 

The weakest bond in a polymer chain determines the overall thermal stability of the polymer molecule. The aliphatic carbon-carbon bond has a relatively low bond energy (see Table 5.1). Oxidation of alkylene groups is also observed during prolonged heating in air. Thus the weak links to be avoided are mostly those present in alkylene, alicyclic, unsaturated, and nonaromatic hydrocarbons. On the other hand, the functions proven to be desirable are aromatic (benzenoid or heterocyclic) ether, sulfone, and some carboxylic acid derivatives (amide, imide, etc.). Aromatic rings in the polymer chain also give intrinsically stiff backbone. 

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